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Assemblages: Modules with Interfaces for Dynamic Linking and Communication Yu David Liu and Scott F. Smith The Johns Hopkins University Assemblages:Modules with InterfacesforDynamic Linking and Communication p.1 The Main Design Principle

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SLIDE 1

Assemblages: Modules with Interfaces for Dynamic Linking and Communication

Yu David Liu and Scott F. Smith The Johns Hopkins University

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.1

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SLIDE 2

The Main Design Principle Every form of interaction of code with the environment should be supported by explicit, declared interfaces.

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.2

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SLIDE 3

A Typical Module

Examples: Functors, Mixins

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.3

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SLIDE 4

Modern Language Interactions

Main forms of interaction include

  • Code-code interaction via static linking
  • Code-runtime interaction via dynamic

linking

  • Runtime-runtime interaction via

distributed messaging

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.4

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SLIDE 5

Our Approach: Assemblages

✁

A module-centric approach to interfaces for all three

✁

Static linking of assemblages—mostly standard stuff

✁

Main contributions: – Module-centric view of dynamic extensibility and distributed messaging – Unified treatment of all three, using related notions

  • f interface

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.5

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SLIDE 6

Code and Runtime

✁

Assemblages are code units—modules

✁

Assemblage runtimes are loaded assemblages

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.6

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SLIDE 7

Static Linking Illustrated

Assemblages with static linkers being linked together:

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.7

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SLIDE 8

Static Linking Illustrated

Assemblages with static linkers being linked together:

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.7

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SLIDE 9

Static Linking Illustrated

Assemblages with static linkers being linked together:

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.7

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SLIDE 10

Dynamic Linking

Gaussian cano Sensing Main

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.8

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SLIDE 11

Dynamic Linking

Gaussian cano Sensing Main

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.8

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SLIDE 12

Dynamic Linking

Gaussian cano Sensing Main h1

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.8

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SLIDE 13

Rebindability of Dynamic Linkers

✁

Problem: The need to allow arbitrary code extension vs Fact that only a fixed number of dynamic linkers can be

  • n an assemblage
✁

Solution: – Allow multiple simultaneous linkings on a single dynamic linker – Get a different name ("handle") to access each one – Unlinking is implicit via garbage collection when handle is unreachable – Use of handles also avoids an “unlinked” error – if you have a handle, it references a real plugin

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.9

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SLIDE 14

Rebindability illustrated

Gaussian cano Sensing Main h1

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.10

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SLIDE 15

Rebindability illustrated

Poisson Gaussian cano Sensing Main h1

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.10

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SLIDE 16

Rebindability illustrated

Poisson Gaussian cano Sensing Main h1 h2

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.10

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SLIDE 17

Rebindability illustrated

Poisson Gaussian cano Sensing Main Non-Parametric h1 h2

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.10

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SLIDE 18

Rebindability illustrated

Poisson Gaussian cano Sensing Main Non-Parametric h1 h2 h3

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.10

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SLIDE 19

Dynamic Linking Tree

Poisson Gaussian cano Sensing Main Non-Parametric h1 h2 h3

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.11

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SLIDE 20

Dynamic Linking Tree

Poisson Gaussian cano Sensing Main Expt1 Non-Parametric h1 h2 h3

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.11

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SLIDE 21

Dynamic Linking Tree

Poisson Gaussian cano Sensing Main Non-Parametric Non-Parametric Expt1 h1 h2 h3

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.11

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SLIDE 22

Dynamic Linking Tree

Poisson Gaussian cano Sensing Main Non-Parametric Expt1 Non-Parametric h1 h2 h3 h4

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.11

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SLIDE 23

Dynamic Linking Tree

Poisson Gaussian cano Sensing Main Non-Parametric Expt1 Non-Parametric Expt2 h1 h2 h3 h4

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.11

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SLIDE 24

Dynamic Linking Tree

Poisson Gaussian cano Sensing Main Non-Parametric Expt2 Expt1 Non-Parametric h1 h2 h3 h4 h5

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.11

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SLIDE 25

Connectors for Messaging

✁

Connectors allow different assemblage runtimes to interact

✁

Aim is a cleaner notion to replace RMI/RPC – RMI/RPC lacks a declared interface of interaction

✁

Connectors in programming languages are not completely new – Previously used in e.g. Cells and ArchJava and Darwin

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.12

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SLIDE 26

Distributed Messaging Illustrated

✂ ✄ ☎

cano Sensing Main

✆ ✝ ✞

p Sensor 1

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.13

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SLIDE 27

Distributed Messaging Illustrated

✂ ✄ ☎

cano Sensing Main

✆ ✝ ✞

p Sensor 1

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.13

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SLIDE 28

Distributed Messaging Illustrated

✂ ✄ ☎

cano Sensing Main

✆ ✝ ✞

p Sensor 1 hc1

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.13

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SLIDE 29

Distributed Messaging Illustrated

✂ ✄ ☎

cano Sensing Main

✆ ✝ ✞

p Sensor 2

✆ ✝ ✞

p Sensor 1

✆ ✝ ✞

p Sensor 3 hc1

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.13

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SLIDE 30

Distributed Messaging Illustrated

✂ ✄ ☎

cano Sensing Main

✆ ✝ ✞

p Sensor 2

✆ ✝ ✞

p Sensor 1

✆ ✝ ✞

p Sensor 3 hc1 hc3 hc2

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.13

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SLIDE 31

Data Encapsulation

Goal: maintain sanctity of the runtime interfaces

✁

Only access internals of a runtime through its interfaces

✁

RMI/RPC violate the sanctity of interfaces – Object references can be passed around – No external interface on modules for potential RMI interactions Thus we enforce the following

✁

No passing of object references across the network

✁

Objects can be copied, but only if their code is already plugged in on the other side

✁

Runtime references can be passed

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.14

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SLIDE 32

The Unification

✟ ✠ ✡ ✠☛ ✡ ☞✌ ✍✎ ✏ ✑ ✒ ✓ ✍ ✌ ☞ ✡ ☞ ☛ ☞ ✎ ✍✎ ✏ ✑ ✒ ✓ ✔ ✠ ✡ ✕ ☞✌

kLib

✖ ✠✗ ✘ ✙ ✏ ✠ ✌

y

✖ ✠✗ ✘ ✚ ✠ ✘ ☞✌ ✡ ✛ ☞ ✎ ☛ ✜ ✓ ☞ ✢ ✠ ✓✣ ✒ ✓ ✑ ✤

ain

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.15

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SLIDE 33

The Unification

✟ ✠ ✡ ✠☛ ✡ ☞✌ ✍✎ ✏ ✑ ✒ ✓ ✍ ✌ ☞ ✡ ☞ ☛ ☞ ✎ ✍✎ ✏ ✑ ✒ ✓ ✔ ✠ ✡ ✕ ☞✌

kLib

✖ ✠✗ ✘ ✙ ✏ ✠ ✌

y

✖ ✠✗ ✘ ✚ ✠ ✘ ☞✌ ✡ ✛ ☞ ✎ ☛ ✜ ✓ ☞ ✢ ✠ ✓✣ ✒ ✓ ✑ ✤

ain

✔ ✠ ✡ ✥ ✒✦ ✌ ✜ ✌

y

✔ ✠ ✡ ✕ ☞✌

kLib

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.15

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SLIDE 34

The Unification

✧ ★ ✩ ★✪ ✩ ✫✬ ✭✮ ✯✰ ✱ ✲ ✭ ✬ ✫ ✩ ✫ ✪ ✫ ✮ ✭✮ ✯ ✰ ✱ ✲ ✳ ★ ✩ ✴ ✫✬

kLib

✵ ★✶ ✷ ✸ ✯ ★ ✬

y

✵ ★✶ ✷ ✹ ★ ✷ ✫ ✬ ✩ ✺ ✫ ✮ ✪ ✻ ✲ ✫ ✼ ★ ✲✽ ✱ ✲ ✰ ✾

ain

✳ ★ ✩ ✿ ✱❀ ✬ ✻ ✬

y

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.15

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SLIDE 35

The Unification

❁ ❂ ❃ ❂❄ ❃ ❅❆ ❇❈ ❉❊ ❋
  • ❇
❆ ❅ ❃ ❅ ❄ ❅ ❈ ❇❈ ❉❊ ❋
  • ❍
❂■ ❏ ❑ ❉ ❂ ❆

y

❍ ❂■ ❏ ▲ ❂ ❏ ❅❆ ❃ ▼ ❅ ❈ ❄ ◆
  • ❅
❖ ❂
  • P
❋
  • ❊
◗

ain

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.15

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SLIDE 36

The Code

❘❚❙ ❯❚❱❲ ❳ ❙ ❨ ❲ ❩ ❳ ❬

// Volcano sensor example

❭❪ ❪❫ ❴ ❵❛ ❭❜ ❫ ❝ ❪ ❞ ❭ ❞ ❡❣❢ ❛ ❡✐❤ ❥ ❫ ❦ ❧❚♠ ♥ ♦ ❩ ♣ ❝

. . . statically linking some network library . . .

q r✐s ❤ ❭ ❴ ❡❣❢ ❛ ❡ ❤ ❥ ❫ ❦ t ♠ ♥ ♠ ❱ ♥ ❙ ✉ ✈ ❯✐✇ ① ❩ ❳ ❝ ❡ ❴② ③ ❦ ❞ ④ ♠ ♥ ♠ ❱ ♥ ❨ ♠ ♥ ⑤ ❙ ④ ⑥⑦ ❫ ⑧ ② ③ ❦ ❞ ① ♠ ♥ ⑨ ❳ ⑩ ❬ ❬

. . . get current environment snapshot . . .

q ❢ ③ ❤ ❤ ❫ ❢ ❞ ③ ❦ ❶ ❙ ④ ♠ ❷❣❸ ④ ❲ ♥ ♠ ❝ ❡ ❴② ③ ❦ ❞ ① ♠ ♥ t ♠ ♥ ♠ ❱ ♥ ❶ ❙ ④ ♠ ⑥ ⑦❺❹ ❫ ⑧ ② ③ ❦ ❞ ❱ ⑤ ♠ ❱ ❻ ⑥❽❼❾ ❿ ➀ ➁ ➂ ➁ ❾ ❿ ⑦ ❬ ❬

. . . check applicability of detect model . . .

q ➃ ➃ ➃

// local feature implementation

✇ ❸ ④ ❲ ♥ ♠ t ♠ ♥ ♠ ❱ ♥ ❙ ✉ ❬ ❬ ➄➆➅ ➃ ⑥ ❛ ❫ ❞ ❼ ➇ ❬ ❢ ③ ❤ ❤ ❫ ❢ ❞➉➈➋➊ ➌➎➍ ➏➋➐ ➌➎➑ ➒ ➍ ➓ ➔ ➈➋➊ ➌➎➍ ➅ ❡✐❤ ❛ ❫ ❞ ❼❾ ➀➆→ ❬ ❼ ➇➋➣ ① ♠ ♥ t ♠ ♥ ♠ ❱ ♥ ❶ ❙ ④ ♠ ↔ ⑥⑦ ❡ ❤ ❛ ❫ ❞ ❼❾ ↕➙ ❬ ② ❛❣➛ ❜ ❡✐❤ ➜ ➍ ➒ ➍➝ ➒ ➊ ➞ ➟➠➢➡ ➤ ➥➋➦ ➓ ➔ ➜ ➍ ➒ ➍➝ ➒ ❼❾ ➀➆→ ❡✐❤ ❼❾ ↕ ➙ ➃ ④ ♠ ♥ ♠ ❱ ♥ ❨❚♠ ♥ ⑤ ❙ ④ ⑥⑦ ⑦ ➃ ➃ ➃ q

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.16

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SLIDE 37

The Type System

✁

Static linkers, dynamic linkers, and connectors are typed

✁

Each import/export is typed

✁

There may be more exports than imports (subtyping)

✁

Assemblage runtime types are the connector types

✁

First-class assemblage types are static/dynamic linkers and connector types

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.17

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SLIDE 38

Technical Accomplishments

✁

Formal operational semantics

✁

Type system

✁

Soundness via a subject reduction argument – Significant extra complication here due to multiple runtimes, modules as first-class values etc

✁

Extension to have types as features on linkers (not proved sound)

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.18

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SLIDE 39

Related Work

Explicit interfaces are there to some degree

✁

Static linking – “solved” in many module systems/calculus.

✁

Dynamic linking – Java classloaders: not explicit; very fine-grained – Units, Argus, MJ, etc have partial interface support

  • n code being linked, but not on the runtime
✁

Distributed langauge-based messaging – Existing protocols bury interactions in the code – RPC/RMI: When remote objects are passed between JVM’s, you don’t even know who you are talking to – Connectors

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.19

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SLIDE 40

Future Work

✁

Implementation

✁

Ensemble: A connector-based Sensornet language

✁

MVM: a Microkernel Virtual Machine

✁

Extensions – Inference of signatures from assemblages – Linker- and connector-based security – Version control

Assemblages:Modules with InterfacesforDynamic Linking and Communication – p.20